N-substituted amine compound is a kind of very useful chemical intermediate, which is widely used in the production of dyes, synthetic resins, medicines, and pesticides. It is well known that amine compounds may be produced in large scale in relatively low cost, and the modern industrial production technology of amine compounds has been founded. Therefore, the method for producing N-substituted amine compounds through the coupling reaction between amines and alcohols or the coupling reaction between amines and amines is a route which is very environmental friendly and attracts lots of interests.
Producing N-substituted amine compounds through the alkylation of amines has been researched for several decades, and a serious of catalysts and synthesis methods have been developed. The reaction between diethylene glycol and methylamine has been catalyzed by a precipitated catalyst consisted of CuO/ZnO under the condition of 150-400° C., and 30-400 bar (GB-B-1106084). Another diatomite-supported nickel catalyst shows good catalytic activity for the reaction for producing N-methylmorpholine from diethylene glycol and methylamine under the condition of 225-250° C. and 100 bars, the yield of which achieves 20-60% (U.S. Pat. No. 3,709,881). Patent EP-A-0440829 discloses a precipitated catalyst of cuprum and aluminum which is added with equivalent alkali for the synthesis of N-substituted cyclic amines from glycols and alkyl amines. Another kind of cuprum magnesium silicate, added with 0-2% mass percentage of BaO, Cr2O3, and ZnO, shows a catalytic activity for the reaction between alkyl amines or dialkyl amines and alcohols at a hydrogen gas pressure of 200 bars to produce N-substituted alkyl amines (U.S. Pat. No. 5,917,039). U.S. Pat. No. 8,071,302 reports an acid zeolite for the reaction between aniline and lower alcohols under the condition of 300-500° C., to selectively produce p-alkyl aniline. U.S. Pat. No. 5,068,434 reports a zeolite with a silicon-aluminum ratio of at least 60 for producing aniline N-alkylation product at 260-330° C. U.S. Pat. No. 5,847,131 reports a Cu catalyst for the N-substitution reaction of alicyclic amines by employing glycols under the condition of 220-280° C. and 100-300 bars, and the catalyst is produced by soaking the SiO2 carrier into an alkali solution with Cu mass percentage of 5-50%. In U.S. Pat. No. 4,268,458, using POCl3 as the catalyst, aniline and aliphatic alcohols or alicyclic alcohols react at 280° C. and a pressure of 60-100 bars to produce 40-90% of N-substituted amine compounds.
Throughout the above various reports, generally, the yield of the product is low, a condition of high temperature and high pressure is generally required, and especially, the problem of the recovery and reuse of the catalyst has not been satisfactorily solved. Therefore, aiming at industrial application, there is strong desire for developing a catalyst for N-substituted amine compounds with high efficiency and ease for recovery and reuse.